Infinitely variable overdrive transmission mechanism

ABSTRACT

A planetary gear mechanism having multiple ratios, at least one of which is an underdrive ratio, including an overdrive unit acting in cooperation with the gearing to provide an overdrive range wherein the overdrive unit is located at the power input side of the gearing where it is adapted to provide a torque delivery path between the torque input elements of the gearing and the power input portions of the mechanism with an infinitely variable speed ratio, the overall speed ratio of the gear system during operation in one limiting ratio in the overdrive range being close to the direct drive ratio of unity.

United States Patent Leonard [451 Sept. 5, 1972 [541 INFINITELY VARIABLEOVERDRIVE TRANSMISSION MECHANISM [72] Inventor: Allan S. Leonard,Livonia, Mich. [731 Assignee: Ford Motor Company, Dearborn,

Mich.

[221 Filed: April 26, 1971 21 Appl. No.: 137,375

[52] U.S. Cl ..74/690, 74/688 [51] Int. Cl ..F16h 37/06 [58] Field ofSearch ..74/690, 691

[56] References Cited UNITED STATES PATENTS 2,164,504 7/ 1939 Dodge..74/690 2,716,357 8/1955 Rennerfelt ..74/691 3,203,278 8/1965 General..74/691 X 3,204,476 9/ 1965 Rouverol ..74/690 X 3,238,816 3/1966Schottler ..74/690 3,494,224 2/1970 Fellows et a1 ..74/691 3,545,302 12/l 970 Schofield ..74/691 3,620,101 11/1971 Abbott et al ..74/691 PrimaryExaminer-Carlton R. Croyle Assistant Examiner-Thomas C. PerryAttorney-John R. Faulkner and Donald J. Harrington [57] ABSTRACT Aplanetary gear mechanism having multiple ratios, at least one of whichis an underdrive ratio, including an overdrive unit acting incooperation with the gearing to provide an overdrive range wherein theoverdrive unit is located at the power input side of the gearing whereit is adapted to provide a torque delivery path between the torque inputelements of the gearing and the power input portions of the mechanismwith an infinitely variable speed ratio, the overall speed ratio of thegear system during operation in one limiting ratio in the overdriverange being close to the direct drive ratio of unity.

4 Claims, 5 Drawing Figures PATENTEDSEP 5 I972 SHEET 3 BF 3 mi 2 N I MWm 4 J. M. y

INFINITELY VARIABLE OVERDRIVE TRANSMISSION MECHANISM GENERAL DESCRIPTIONOF THE INVENTION This invention relates to the disclosure of co-pendingapplication Ser. No. 137,374, filed Apr. 26, 1971. That co-pendingdisclosure, as well as this disclosure, deals with overdrive powertransmission mechanisms wherein an infinitely variable overdrive unitacts in cooperation with the planetary gear elements of a planetary gearsystem, the latter acting to provide at least one underdrive ratio, areverse ratio and a direct drive ratio while the overdrive unit isinactive. If an upshift from the direct drive ratio to the overdriverange is desired, a reaction brake for the overdrive unit may be appliedso that its elements may cooperate with gear elements to provide anoverdrive speed ratio range wherein the overdrive ratio may beinfinitely varied between two operating limits, the lowermost limitproviding an overall ratio equal to or only slightly greater than thedirect drive ratio of unity. In the particular embodiment disclosedhere, the overdrive unit is a ball friction unit situated between thegearing and a hydrokinetic torque converter at the power input end ofthe transmission. When it is so situated, it is subjected to a lowertorque level than the torque level to which it would be subjected if itwere located at the torque output end of the transmission mechanism.

The transmission mechanism of my invention is adapted especially for usein an automotive vehicle having an internal combustion engine. Theoverdrive ratio is available during cruising operation understeady-state operating conditions. The infinitely variable overdriveratio characteristic prevents frequent hunting between the direct driveratio of the gearing and the overdrive ratio as the road load changeswith the vehicle operating in the overdrive range. If a change in roadload should be experienced with the transmission in the overdrive range,the ratio characteristics of the overdrive unit will vary to accommodatethe changes in road load. The overdrive unit is used in conjunction withan auxiliary planetary gear to reduce the torque capacity requirementson the infinitely variable overdrive unit. Since the torque level forthe overdrive unit is reduced, the reliability of the unit as well asthe infinitely variable ratio controls is improved.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS FIG. 1 shows inschematic form the torque delivery elements of one embodiment of myinvention;

FIG. 2 is a chart showing the speeds of the torque delivery elements ofthe gear system of FIG. 1 relative to the speed of the input shaft;

FIG. 3 is a modified form of my invention which differs from theembodiment of FIG. 1 by the dual split torque delivery path between thetorque converter and the input side of the overdrive unit;

FIG. 4 is a chart showing the speeds of rotation of the torque deliveryelements of the gear system of FIG. 3 relative to the speed of the inputshaft;

FIG. 5 is a diagram showing the geometry of the friction overdrive unitused in the embodiments of FIGS. 1 and 3.

PARTICULAR DESCRIPTION OF THE INVENTION Numeral l0 designates the end ofa crank shaft of an internal combustion engine. Numeral 12 designatesthe power output shaft of the transmission mechanism. It may beconnected drivably to the vehicle traction wheels through a suitabledrive shaft and differentialand-axle assembly.

Shaft 10 is connected to a bladed impeller 14 of a hydrokinetic torqueconverter unit 16. Unit 16 includes also a bladed turbine 18 and abladed stator 20. The impeller,the turbine and the stator are located intoroidal fluid flow relationship in the usual fashion.

Turbine 18 is connected drivably to turbine shaft 22, which serves as atorque input shaft for the gearing.

The gearing includes two simple planetary gear units 24 and 26 and anauxiliary gear unit 28, the latter forming a part of the overdrivemechanism. Gear unit 24 includes a carrier 30, which is connecteddirectly to the power output shaft 12. Gear unit 24 includes also ringgear 32, sun gear 34 and planet pinions 36 joumalled on carrier 30 sothat they mesh with gears 32 and 34.

Gear unit 26 includes sun gear 38, which is connected to or formedintegrally with sun gear 34. Gear unit 26 includes also a ring gear 40,which is connected to power output shaft 12. Carrier 42 of gear unit 26journals pinions 44 which mesh with gears 38 and 40. Carrier 42 isbraked against the transmission housing through an overrunning brake 46so that it may act as a reaction member during low speed ratio,forward-drive operation. Carrier 42 is connected to brake drum 48 aboutwhich is positioned brake band 50. During low speed ratio, hill-brakingoperation, brake band 50 is applied. It is applied also during operationin reverse.

Intermediate speed ratio operation is accomplished by engaging brakeband 52 which surrounds brake drum 54. Sun gears 34 and 38 are connecteddrivably to brake drum 54.

Turbine shaft 22 is connecteddrivably to the ring gear 32 throughforward drive clutch 56. This clutch is engaged during operation in eachforward drive ratio. Shaft 22 is connected drivably to the sun gearsthrough selectively engageable clutch 58 which is applied duringoperation in high speed ratio and during reverse drive operation.

The overdrive unit is designated by reference character 60. It includesa carrier 62 which is connected directly to the turbine shaft 22. Theseries of balls 64 are supported by the carrier 62. The balls 64 mayrotate about their axes, and the carrier 62 is adapted to accommodatechanges in radial position of the balls with respect to the shaft 22.

The balls 64 frictionally engage a pair of outer races 66 which contactthe balls 64. The contact between the balls 64 and races 66 is pointcontact along the rolling circle. Similarly, balls 64 engage inner races68 along the rolling circle. The surfaces of the races that engage theballs are concave and have a radius of curvature greater than the radiusof the balls. As the races 66 are moved axially with respect to eachother and as races 68 are moved axially in unison with the axialadjustment of races 66, the effective rolling radius of the balls ischanged.

Outer races 66 are connected to brake drum 70 about which is positioneda reaction brake band 72.

Brake band 72 can be applied to anchor races 66, thereby .overspeedingthe inner races 68 as carrier 62 acts as a torque input member. Races 68in turn are connected to ring gear 74 of gear unit 28, the connectionbeing provided by a sleeve shaft 76. Sun gear 78 of gear unit 28 isanchored to the transmission housing as shown at 80. Carrier 82 of gearunit 28 carries pinions 84 which engage ring gear 74 and sun gear 78.Carrier 82 is connected directly to brake drum 54.

During operation of the transmission in the overdrive range, clutch 58is released and turbine torque from shaft 22 is distributed throughengaged clutch 56 to the ring gear 32. A portion of the turbine torqueis distributed to carrier 62. Brake band 72 is applied during overdriveoperation, thereby causing ring gear 74 to be overdriven by the races68. This imparts a forward driving motion to the sun gear 34, theangular velocity of gear 34 being greater than engine speed. Thisprovides an overall torque ratio less than unity.

It is possible for the infinitely variable unit to operate with a speedratio that will result in an effective overall ratio very close to unityat the minimum overdrive end of the overdrive operating range. This isapparent from inspecting the relative speeds in the second column of thechart of FIG. 2. The overall speed ratio can be changed, however, byvarying the infinitely variable ratio of the overdrive unit so that theeffective relative speed of the driven member is about 1.8 times thespeed of the shaft 22. The torque distributed through the infinitelyvariable unit is of a reduced magnitude because it is situated ahead ofthe torque transmitting gearing and because it is adapted to receiveonly a part of the input torque, the remaining part of the input torquebeing distributed directly through the clutch 56 to the input ring gear32.

FIG. 5 shows schematically the geometric configuration of the balls andthe races. The balls adapt and engage races at a point of contact havingan angular disposition with respect to a horizontal reference line asshown by angle ar. If the angle a,., upon axial adjustment of the races,equals approximately 65, the overdrive ratio will be very close tounity. On the other hand, if the races are adjusted so that the angle a,equals approximately 24, the output shaft speed during overdriveoperation will equal about 1.8 times the speed of the shaft 22.

FIG. 3 shows an alternate embodiment of the invention. It differs fromthe concept of FIG. 1 insofar as the torque flow path to the infinitelyvariable unit is concerned. Each of the elements of FIG. 5 that has acounterpart in the structure of FIG. 1 has been designated by similarcharacters, although prime notations have been added.

In the FIG. 3 embodiment the sun gear 78' is anchored by the brake band72. During overdrive operation the same brake band 72 anchors the outerraces 66' of the overdrive unit 60'. The torque converter 16' of themechanism of FIG. 3 has an impeller which is connected directly to thecarrier 62' of the overdrive unit 60. This connection is establishedthrough a driving member 85, which includes drive struts extendingthrough the torus circuit of the converter. Driving member 85establishes a direct connection between the impeller and carrier 62 sothat impeller torque is distributed to the input side of overdrive unit60'. Turbine torque on the other hand is distributed directly fromturbine 18' through turbine shaft 22. During overdrive operation theturbine torque is distributed then through engaged clutch 56' to thering gear 32. Thus a split torque delivery path is established althoughthe portion of the torque being distributed through the overdrive gearunit is distributed through a mechanical torque delivery path ratherthan through the hydrokinetic unit.

The chart of FIG. 4 is similar to the chart of FIG. 2. It indicates thespeeds of the torque delivery elements of FIG. 3 relative to the speedof the engine. Two values for relative speeds are represented in FIG. 4for the overdrive range. The first value represents the lowest overdriveratio available in the overdrive range and the second value representsthose speeds when the overdrive unit is operating at its upper limit.

Having thus described two embodiments of my invention, what I claim anddesire to secure by U.S. Letters Patent is:

1. A multiple ratio power transmission mechanism having an infinitelyvariable overdrive capability comprising planetary gear elements; adriven shaft connected to a power output gear element; brake means foranchoring a second gear element to provide torque reaction duringunderdrive ratio operation; first clutch means for connecting a powerinput shaft to a power input gear element; an overdrive unit comprisinga reaction member, a torque output member and a torque input member;means for distributing a portion of the torque of said power input shaftto the torque input member of said overdrive unit; an auxiliary gearunit comprising a ring gear, a sun gear and a planet carrier; means foranchoring the sun gear of said auxiliary gear unit during overdriveoperation, a torque output element of said overdrive unit beingconnected to the ring gear of said auxiliary unit; the carrier of saidauxiliary unit being connected to a second power input gear elementduring overdrive operation thereby increasing the overall speed ratio,and means for varying the torque ratio of said overdrive unit between afirst operating value which results in an overall speed ratio close tounity and a second operating value which results in overall speed ratiossubstantially greater than unity.

2. The combination as set forth in claim 1 wherein said overdrive unitcomprises a ball friction drive having a series of torque transmittingballs; a carrier registering with said balls; said carrier being adaptedto function as said torque input member for said overdrive unit;adjustable outer races frictionally contacting said balls at locationsspaced radially inwardly from the points of contact between said ballsand said outer races; and brake means for anchoring the outer racesduring overdrive operation whereby the inner races are overdriven, saidinner races being connected directly to the ring gear of said auxiliaryunit.

3. The combination as set forth in claim 1 wherein the torque inputmember of said overdrive unit is connected directly to said power inputshaft; the driving connection between said power input shaft and saidpower input gear element including a hydrokinetic turbine situated inparallel disposition with respect to the driving connection between saidpower input shaft and the carrier of said overdrive unit wherebyparallel input bine situated in parallel disposition with respect to thedriving connection between said power input shaft and the carrier ofsaid overdrive unit whereby parallel input torque delivery paths areprovided; one of which is a hydrokinetic path and the other of which isa solid mechanical path.

1. A multiple ratio power transmission mechanism having an infinitelyvariable overdrive capability comprising planetary gear elements; adriven shaft connected to a power output gear element; brake means foranchoring a second gear element to provide torque reaction duringunderdrive ratio operation; first clutch means for connecting a powerinput shaft to a power input gear element; an overdrive unit comprisinga reaction member, a torque output member and a torque input member;means for distributing a portion of the torque of said power input shaftto the torque input member of said overdrive unit; an auxiliary gearunit comprising a ring gear, a sun gear and a planet carrier; means foranchoring the sun gear of said auxiliary gear unit during overdriveoperation; a torque output element of said overdrive unit beingconnected to the ring gear of said auxiliary unit; the carrier of saidauxiliary unit being connected to a second power input gear elementduring overdrive operation thereby increasing the overall speed ratio,and means for varying the torque ratio of said overdrive unit between afirst operating value which results in an overall speed ratio close tounity and a second operating value which results in overall speed ratiossubstantially greater than unity.
 2. The combination as set forth inclaim 1 wherein said overdrive unit comprises a ball friction drivehaving a series of torque transmitting balls; a carrier registering withsaid balls; said carrier being adapted to function as said torque inputmember for said overdrive unit; adjustable outer races frictionallycontacting said balls at locations spaced radially inwardly from thepoints of contact between said balls and said outer races; and brakemeans for anchoring the outer races during overdrive operation wherebythe inner races are overdriven, said inner races being connecteddirectly to the ring gear of said auxiliary unit.
 3. The combination asset forth in claim 1 wherein the torque input member of said overdriveunit is connected directly to said power input shaft; the drivingconnection between said power input shaft and said power input gearelement including a hydrokinetic turbine situated in paralleldisposition with respect to the driving connection between said powerinput shaft and the carrier of said overdrive unit whereby parallelinput torque delivery paths are provided; one of which is a hydrokineticpath and the other of which is a solid mechanical path.
 4. Thecombination as set forth in claim 2 wherein the torque input member ofsaid overdrive unit is connected directly to said power input shaft, thedriving connection between said power input shaft and said power inputgear element including a hydrokinetic turbine situated in paralleldisposition with respect to the driving connection between said powerinput shaft and the carrier of said overdrive unit whereby parallelinput torque delivery paths are provided; one of which is a hydrokineticpath and the other of which is a solid mechanical path.